Apparatus and method of utilizing the conversion of parahydrogen to orthohydrogen to obtain a refrigerating effect



July 10, 1962 J. E. AHERN 3,043,110

APPARATUS AND METHOD OF UTILIZING THE CONVERSION OF PARAHYDROGEN To ORTHOHYDROGEN TO OBTAIN A REFRIGERATING EFFECT Filed Jan. 26, 1961 4 Sheets-Sheet 1 JNVENTOR. JOHN E. AHERN Attorney July 10, 1962 J. E. AHERN 3,043,110

APPARATUS AND METHOD OF UTILIZING THE CONVERSION OF PARAHYDROGEN T0 ORTHOHYDROGEN TO OBTAIN A REFRIGERATING EFFECT Filed Jan. 26, 1961 4 Sheets-Sheet 2 I6 I l7 l8 24 3o 1 00 7 00-0 000' E 000000 0 0000000 0 000000070 g 15 7 l8 [8 L9 10 23 FIG. 2

INVENTOR.

Attorney July 10, 1962 J. E. AHERN 3,043,110

APPARATUS AND METHOD OF UTILIZING THE CONVERSION GEN TO ORTHOHYDROGEN T0 OF PARAHYDRO OBTAIN A REFRIGERATING EFFECT 4 Sheets-Sheet 3 Filed Jan. 26, 1961 Tempe ruture,

FIG. 4

INV ENTOR. JOHN ;E. AHERN Attorney July 10, 1962 J. E. AHERN 3,043,110

APPARATUS AND METHOD OF UTILIZING THE CONVERSION OF PARAHYDROGEN TO ORTHOHYDROGEN TO OBTAIN A REFRIGERATING EFFECT Filed Jan. 26, 1961 4 Sheets-Sheet 4 2 IIXII 2 m 200 r E Equilibrium 2 Hydrogen I: m 150 .E 95% Para Hydrogen h 60 7O 8O 90 I00 "0 I20 Temperature, "R

F G 6 INVENTOR. JOHN -sAHERN Attorney APPARATUS AND METHOD OF UTILIZENG THE CONVERSION F PARAHYDROGEN T0 QR- TI-IOHYDROGEN TO OBTAIN A REFRIGERAT- HIG EFFECT John E. Ahern, Granada Hills, Calif, assignor to The Marquardt Corporation, Van Nuys, Calih, a corporation of California Filed Jan. 26, 1961, Ser. No. 85,133 12 Claims. (Cl. 624) This invention relates to an apparatus and method for utilizing the conversion of parahydrogen to orthohydrogen to obtain a refrigerating effect and more particularly relates to a heat exchange apparatus and method of operation in which hydrogen is introduced in para form and catalytically converted to the ortho form between passes in the heat exchanger.

Liquid hydrogen, because of its low boiling point (36.7 R.) and its high specific heat, has a very great cooling capacity as a refrigerant. At low temperatures, liquid hydrogen can exist in two forms known as orthohydrogen and parahydrogen. The para form is the most stable in the liquid state and therefore, when liquid hydrogen is produced, it is catalytically converted to about 95 percent para form although additional heat must be removed to bring about the conversion process. If this conversion were not done, the liquid hydrogen would by itself slowly convert to the more stable para form and in doing so would release enough heat to boil off a large part of the liquid hydrogen since the conversion is an exothermic process. The equilibrium content of the para form decreases as the temperature of the hydrogen increases, but a catalyst is required to have this conversion take place at a reasonably fast rate. During this conversion from para to ortho hydrogen, heat is absorbed and therefore additional coolant capacity is realized.

The present invention contemplates that some parahydrogen be converted by catalyst to orthohydrogen through an adiabatic conversion which can be accomplished in steps as the hydrogen warms up. This stepwise conversion can be accomplished between the passes of a heat exchanger to obtain optimum refrigerating effeet from the hydrogen coolant. A catalyst chamber is located intermediate one or more passes of the heat exchanger and each chamber has a substantially greater flow area than the passes of the heat exchanger so that the flow velocity of the hydrogen through the catalytic chambers is substantially less than the flow velocity through the heat exchanger passes. Since the catalyst chambers are divorced from the heat exchanger itself, the low velocity flow through the catalyst provides the long time delay which is required for the catalyst, while the flow through the heat exchanger passes is at a high velocity required for good performance of the heat exchanger.

It is therefore an object of the present invention to provide an apparatus and method for obtaining optimum refrigeration effect from liquid hydrogen by converting para to ortho hydrogen with a catalyst intermediate one or more passes of the hydrogen.

Another object of the invention is to provide an apparatus and method of obtaining increased refrigerating effect from liquid hydrogen by passing the hydrogen through a catalyst chamber located intermediate one or more of heat exchanger passes, said catalyst chambers having greater flow area than the heat exchange passes so that the hydrogen has low velocity and long conversion time in the chamber, and high velocity and good heat exchanger performance in each of the passes.

Another object of the invention is to provide an apparatus and method of utilizing the para to ortho con- 3,043,110 Patented July 10, 1962 version of hydrogen to obtain increased refrigeration effects from liquid hydrogen by utilizing step-wise adiabatic conversion of a portion of the parahydrogen to orthohydrogen at points intermediate a heat exchanger.

These and other objects of the invention not specifically set forth above will become readily apparent from the accompanying description and drawings, in which:

FIGURE 1 is a perspective view of a heat exchanger having catalyst converter chambers located between the first and second and the second and third passes and between third and fourth passes.

FIGURE 2 is a horizontal section along line 2-2 of FIGURE 1 illustrating the various passes of the heat exchanger.

FIGURE 3 is a vertical section along line 33 of FIGURE 1 illustrating one of the heat exchanger passes and the catalyst converter chambers at both ends thereof.

FIGURE 4 is a graphic illustration of the step-wise adiabatic conversion of a portion of parahydrogen to orthohydrogen in each of the catalyst chambers of FIG- URE 1.

FIGURE 5 is perspective view of a second form of the invention in which a catalytic converter chamber is located between each of the passes of a heat exchanger to obtain a maximum number of step-wise adiabatic conversions.

FIGURE 6 is a graphic illustration of the step-wise adiabatic conversions taking place in the catalyst chambers of FIGURE 5.

The embodiment of the invention shown in FIGURE 1 comprises a passage 8 to which air or other medium to be cooled is introduced at the entrance end 9. Between the entrance end 9 and the discharge end 10 is located the heat exchanger 11 of the present invention which comprises four separate passes 13, 14, '15, and 16. The passage 8 can be of rectangular cross-section and the tube banks comprising the various passes can be arrayed in the same cross-sectional configuration. The individual tubes 17 in each bank are held separate from one another at each end by suitable headers 18 to permit fluid flow past the tubes, and the headers are secured to passage 8 in any suitable manner. The tubes 17 of the passes 13 and 14 are connected together by curved sections 19 so that these tubes are continuous.

The liquid hydrogen is introduced through passage 20 to the tubes 17 of the first pass 13 and is connected to the second pass 14 by tube sections 19. The hydrogen leaving pass 14 discharges into a catalyst converter chamber 21 which is filled with granules 22 of a catalyst, such as pulverized hydrous ferric oxide or the like, which serves to convert a portion of the parahydrogen entering the heat exchanger 11 to orthohydrogen. A screen 23 is located over the outlet of pass 14 to prevent the catalyst from entering and clogging the tubes of pass 14. Catalyst chamber 21 contains a plurality of curved vanes 24, 25 and 26 which are secured to the sides of the chamber 21 and serve to direct the air flow from the pass 14- through the catalyst chamber and into the tubes of the pass 15. The entrance ends of the tubes of pass 15 are covered by a screen 30 which prevents the catalyst 'in chamber 21 from entering these tubes.

Pass 15 discharges to a second catalyst converter chamber 31 which is identical in construction to chamber 21 and contains pulverized catalyst 22 through which extends another set of turning vanes 24, 25 and 26 and chamber 31 serves to convert another part of the parahydrogen to orthohydrogen prior to the hydrogen entering the tubes of stage 16. The discharge end of pass 15 and the entrance end to pass 16 are covered by screens 36 and 37, respectively, in order to keep the catalyst in chamber 31 from entering the tubes of these stages. Finally, the hydrogen leaves the heat exchanger 11 per-ature.

enters ,theheat exchanger at passage 20 at the condition 7 line dry athrough passage '40 connectingwith the discharge'end of pass 16. It is understood that the'curved vanes'within the catalyst chambers extend completely across the chamular hydrous ferric oxide, which cuts down the available flow space, the flowlarea still exceeds the total tube are-a in each of the passes by a substantial amount. The

hydrogen leaving the last passildthroughthe passage 44) contains an amountof parahydrogen approaching that V of. equilibrium hydrogen The lower flow velocity of p the air passing through each of the catalyst chambers gives the hydrogentime forthe catalystto accomplish the necessary conversion. in each catalyst chamber and the higher velocity flow through the tubes of each of the passes results in good heat exchange performance in the Thefefiect of thercatalyst chambers on the cooling capacity of the hydrogen passing through the heat .exchangerllis illustrated-by the plot of FIGURE 4. The

curve X illustrates the enthalpy per pound of equilibrium hydrogen commencing at the temperature of 60 R.

, whereas the curveY shows the enthalpy per pound of 95 percent parahydrogen commencing at the same tem- Hydrogen whichis 95 percent parahydrogen a of FIGURE 4 and follows the 95 percent para line up to the pointfb at'which point it leaves the pass 14 and enters the catalyst chamber 21. In passing through catalyst'charnber- 21, some parahydrogen is converted adiabatically to orthohydrogen and the horizontal line from b 'to is followed toward equilibrium hydro- -c gen. At point c, the. hydrogen leaves the catalyst a means. The hydrogen leaving pass 45 flows through the catalyst chamber 52 into pass 46 and the hydrogen leaving the pass 46 enters the chamber 53 which discharges into the pass 47. Catalyst chamber 54 is located between the'outlet of pass 47 and the entrance to pass 48 and pass 43 discharges the mixture of ortho and parahydrogen through'the outlet-passage 55. As in the 'prior embodiment, each of the catalyst chambers contains turning vanes 56, 57 and 58 and can be filled with granular hydrous ferric oxide as the catalyst. Since the catalyst is in granular form, the'hydrogen can pass through the spaces between the granules, during which time it is partially converted from para to ortho hydrogen. Also, the entrance and outlet of each of the heat exchanger passes are covered by a screen 61 so that the catalyst cannot enter and plug the tubes in each ofthe passes. While FIGURE 5 illustrates a four-pass heat exchanger the apparatus of FIGURE 5 differs from'the apparatus to FIGURE 1 in "that three instead of two catalyst chambers are utilized.

Referring to FIGURE 6, the enthalpy versus temperature plot for FIGURE 5 is illustrated, along with the line X corresponding to' equilibrium hydrogen and the line-Y corresponding to 95 percent parahydrogen. The

"point a represents the condition at which'the 95 perchamber 21 and flows through the pass of the heat exchanger. where its condition follows the lines c to d. Ata point d, the hydrogen enters catalyst chamber 3.1 and further conversion trom para to ortho towards the equilibriunrline X results in the hydrogen following the to e. At point e, the hydrogen leaves the catalyst chamber i'al and flows through the pass 16 of the r heat exchanger and its condition during this part of its flow is shown by the line e to f. The hydrogen leaves the heat exchanger at the temperature h and enthalpy i. If no catalyst were utilized to convert the parahydrogen to orthohydrogen, the hydrogen leaving the pass 16 of the heat exchanger would be at the condition of point g with a temperature of 120 R. and art It the inlet enthalpy enthalpy designated at point k. is designated as point I, the enthalpy difference between points j and l is greater than the enthalpy diiference between points k and l and thus, a greater cooling capacity is realized for the same temperature difference when using the catalyst chambers of the present invention. The amount of adiabatic conversion along the lines b to c and d to 2 will depend upon a number of factors, such as the effectiveness of the catalyst, the time of contact of the hydrogen with the catalyst, and the hydrogen flow velocity. The factors can be varied as desired to produce the increased cooling capacity desired.

Referring to FIGURE 5, the passage 8 of FIGURE 1 a and the heat exchanger 11' are shown in perspective and a catalyst chamber is utilized between eachpass of the heat exchanger. Air entering the passage 8 at the entrance 9 passes over the heat exchanger passes 45, 46, 47 and 48 and the 95 percent parahydrogen is introduced to the pass 45 through-the inlet passage 49. The heat exchanger 11' differs from the exchanger 11 of FIGURE '1 only because the tube sections 19 have been replaced by another catalyst chamber 5 2. The tubes 50 of the passes are all held separate by header plates 51 located at the V entrance and discharge ends of the passes by suitable of the heat exchanger 11'.

cent parahydrogen enters the pass 45 of theheat exchanger 11 and this condition is the same as point a" in FIGURE 4. The parahydrogen follows the 95 percent up to point m where the hydrogen leaves the pass Passing through the catalyst chamber 52, some parahydrogen is converted adiabatically to orthohydr'ogen along line m to n.

At point n, the hydrogen leavesthe catalyst chamber 52 and flows through the second pass 46 of'the heat exchanger, during which its condition follows the line It to *0. At point 0, the hydrogen enters the second catalyst chamber 53 and again further adiabatic conversion from para to orthohydrogen results -al0ngth6 line The hydrogen enters the third pass 47 of 0 to p. 7 the heat exchanger at point p and follows the line p to q. 7 At point q, the hydrogen enters the catalyst chamber 54' and again further conversion from para t0 orthbhydrogen takes place along the line q to r.

through the last pass .48 of the'heat exchanger, during paratus.

which its condition follows the line r to s.

. than the enthalpy difference between 6 is substantially greater than the enthalpy difference between fk and l which results when no catalyst is utilized to convert para to orthohydrogen. Also, the enthalpy difierence between w and l is even greater and l illustrated in FIGURE 4 for only two catalyst chambers. Thus, it is apparent that the additional chamber of FIG- URE 5 results in more effective cooling thus obtained 'With the apparatus of FIGURE 1. By the present invention, there and apparatus for obtaining optimum refrigeration effect from a coolant consisting of very low temperature hydrogen,.and this cooling is obtained by taking advantage of the adiabatic conversion of para to orthohydrogen. While a four pass heat exchanger with two or three catalyst chambers has been illustrated, it is understood that any number of heatexchanger passes with a varying number of catalyst chambers can be utilized as desired for each application of the invention. With the present invention, good performance can be obtained both in the heat exchanger and in the catalytic converters, and the placing of the catalytic converters between the heat exchanger passes provides minimum volume for the ap- Since easy acce ss is available to the catalyst The hydrogen leaves the chamber 57 at point andflows is provided a method chambers, the catalyst can be inspected and replaced without interfering with the heat exchanger passes. Various other modifications are contemplated by those skilled in the art without departing from the spirit and scope of the invention as hereinafter defined by the appended claims.

What is claimed is:

1. A method of utilizing a source of liquid hydrogen stored in substantially para form as a coolant comprising the steps of introducing the hydrogen in series to a plurality of heat exchange passes, and passing the hydrogen through a catalyst located between one or more pairs of said passes to adiabatically convert a portion of the parahydrogen to orthohydrogen and thereby lower the temperature of the hydrogen.

2. A method of utilizing liquid hydrogen stored as mainly parahydrogen for a coolant comprising the steps of introducing the hydrogen in series to a plurality of heat exchanger passes, passing said hydrogen through one or more enlarged chambers located between one or more pair of passes of said heat exchanger, and placing in each chamber a catalyst for converting parahydrogen to orthohydrogen, the hydrogen flow velocity through each chamber being substantially less than the hydrogen flow velocity through each of the passes.

3. A method as defined in claim 2 wherein the hydrogen is passed through four separate heat exchanger passes and is passed through two separate catalytic chambers located between the second and third passes and between the third and fourth passes.

4. A method as defined in claim 2 wherein the hydrogen is passed through four separate heat exchanger passes and is passed through three catalytic chambers located between first and second, second and third, and third and fourth passes.

5. A method as defined in claim 2 including the step of placing pulverized hydrous ferric oxide in each chamber to serve as the catalyst.

6. A method of utilizing liquid hydrogen stored as mainly parahydrogen as a coolant comprising the steps of introducing the hydrogen to the first of a plurality of heat exchange passes, removing the hydrogen at the discharge end of one or more of the passes, adiabatically converting a portion of the parahydrogen to orthohydrogen in the removed portion, and thereafter returning the removed portion to the entrance of the following pass, thereby lowering the temperature of the hydrogen at constant enthalpy prior to entering the following pass.

7. A method as defined in claim 6 wherein the hydrogen flow velocity in each chamber is reduced to provide sulficient contact time with the catalyst, the amount of parahydrogen converted to orthohydrogen during each adiabatic conversion being insuflicient to produce equilibrium hydrogen so that the hydrogen coolant always contains more parahydrogen than required for equilibrium hydrogen.

8. A heat exchange apparatus connected with liquid hydrogen as a source of coolant comprising, a pluralityof series connected heat exchange passes over which flows a fluid to be cooled, means for introducing the hydrogen to the first of said passes, means for connecting the discharge end of one or more passes with the entrance end of an adjacent pass, a catalyst contained in each connecting means for converting a part of the parahydrogen entering each connecting means to orthohydrogen and thereby reducing the temperature of the hydrogen coolant at one or more locations intermediate the passes.

9. A heat exchange apparatus as defined in claim 8 wherein said connecting means has larger hydrogen flow area than each of said passes to produce a reduced velocity flow over the catalyst in each connecting means during adiabatic conversion while providing a high velocity flow in the passes.

10. A heat exchange apparatus connected with liquid hydrogen as a source of coolant comprising a duct for a. high temperature fiuid to be cooled by the hydrogen, a plurality of heat exchange passes spaced apart along said duct and each comprising a plurality of tubes extending transversely through said duct, a catalyst chamber connecting the discharge end of one of said passes to the entrance end of the following pass, a catalyst contained within said chamber for adiabatically converting a part of the parahydrogen entering the chamber to orthohydrogen in order to lower the temperature of the hydrogen coolant prior to entering the following pass, the flow area of said chamber being larger than the flow area of each of said passes to provide a substantially lower hydrogen velocity in the chamber than in the heat exchange passes.

11. A heat exchange apparatus as defined in claim 10 wherein said duct is rectangular in shape, said chambers having the same transverse width as duct and extending along the length of said duct to connect the discharge end of one pass with the entrance end of the following pass.

12. A heat exchange apparatus as defined in claim 10 wherein each of said connecting means contains granular hydrous ferric oxide as the catalyst.

Price Jan. 20, 1931 Weitzel et a1 July 5, 1960 

1. A METHOD OF UTILIZING A SOURCE OF LIQUID HYDROGEN STORED IN SUBSTANTIALLY PARA FORM AS A COOLANT COMPRISING THE STEPS OF INTRODUCING THE HYDROGEN IN SERIES TO A PLURALITY OF HEAT EXCHANGE PASSES, AND PASSING THE HYDROGEN 